1. Field of the Invention
The invention relates to a process for the selective removal of H.sub.2 S from a gas mixture containing H.sub.2 S and CO.sub.2, in particular a gas mixture containing a relatively high proportion of CO.sub.2. An example of such a gas mixture is natural gas.
2. Description of the Prior Art
It is known to purify such a gas mixture by contacting it in a contacting zone with a lean and regenerable absorbent, from which zone a purified gas mixture and a loaded absorbent are removed. The loaded absorbent is regenerated in a regeneration zone with the addition of heat in order to obtain a regenerated absorbent and a gas mixture, and the regenerated absorbent is introduced into the first contact zone.
A correct choice of contact zone and absorbent enables the H.sub.2 S to be almost entirely removed and the CO.sub.2 to be partly removed from the gas mixture being purified. The gas mixture obtained on regenerating the absorbent therefore contains CO.sub.2 in addition to H.sub.2 S. Assuming a gas mixture containing 1 volume part of H.sub.2 S to 50 volume parts of CO.sub.2, the gas mixture obtained after regeneration will contain, depending on the absorbent used, 1 volume part of H.sub.2 S to 10-15 volume parts of CO.sub.2.
As the gas mixture obtained after regeneration of the absorbent is led to a Claus unit for recovering sulphur, it is important to keep the quantity of CO.sub.2 in this gas as small as possible.